The present invention relates to a structural and aerodynamic module of a turbomachine casing, for example an intermediate casing of a dual-flow turbine engine for an airplane, to a casing structure comprising a plurality of such a module, and to a turbomachine comprising at least one such casing.
A turbojet engine traditionally comprises, from upstream to downstream, a low-pressure compressor or fan, a high-pressure compressor, a combustion chamber, a high-pressure turbine, and a low-pressure turbine.
Moreover, the turbojet engine comprises an outer casing, an inner casing, and an intermediate casing concentric to the first two casings and dividing the space delimited between the outer and inner casings into a primary stream allocated to the compression, then expansion of the propulsion gases, and a secondary stream in which the secondary air circulates.
The intermediate casing performs a structural function by connecting the inner hub to the outer shroud and being able to support loads during operation. To that end, the intermediate casing comprises rigid radial arms connecting the inner hub to the outer shroud. The shape of the radial arms is determined so that its aerodynamic impact on the flow is as limited as possible.
An aerodynamic flow stationary guide vane in the axis of the engine is also provided. This stationary guide vane is made up of a plurality of stationary vanes, which are called outlet guide vanes (OGV).
In traditional turbojet engines, the flow stationary guide vane or cascade vane is separate from the intermediate casing and is situated upstream thereof. However, it is desirable to reduce the mass of turbojet engines and, as a result, the mass of the elements making them up.
To that end, in the turbojet engines under development, it is provided to combine the intermediate casing and the flow stationary guide vane in order to eliminate a certain number of parts. As a result, the vanes are such that they serve the structural function of radial arms.
Vanes made from a metal material make it possible to perform that function. However, they have a high mass.
Document FR 2 685 383 describes an intermediate casing of a turbomachine comprising structural arms comprising an elongated element made from a composite material and fastening fittings for fastening said elongated element to the inner hub and the outer shroud. The elongated body is made by draping several layers of fibers and comprises a recess filled with support fibers in the longitudinal direction of the arm.
The metal fittings are arranged in the four corners of the elongated element and are fixed thereon by screws and nuts. This type of casing is satisfactory from a structural perspective, but it is complex to produce because it comprises four fittings per structural arm, which multiplies the fastening of each of the arms on the inner hub and the outer shroud. Moreover, the mass of the fittings is non-negligible.